The additive manufacturing technology from HERMLE is based on an approach that is just as fascinating and ingenious. Find more details about how it works and the numerous novel opportunities it provides.
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MPA – metal powder application process
Additive manufacturing using HERMLE MPA technology
We have been focussing on the development of new generative manufacturing techniques for several years now. The industrially matured HERMLE MPA technology represents an innovative and versatile process for the generative production of all metal components and displays its full potential especially in the field of tool and mould making. One of the main advantages is the opportunity to complement pre-cast semi-finished parts with generatively manufactured components. With its large working area and a traverse range measuring 800 - 800 - 550 mm (X-Y-Z), the MPA42 machine sets new standards.
MPA = Metal Powder Application
The HERMLE MPA technology is a kinetic spray process that uses metal powder to build up solid components layer by layer. To do so, powder particles are accelerated to very high speeds by means of a carrier gas and then deposited on the substrate via a nozzle. Buildup rates of up to 900 ccm/h and a powder jet from the nozzle comprising several millimetres ensure the MPA technology creates a comparatively dense layer of material on components of varying sizes.
Material build-up and machining combined
The MPA application unit with the nozzle is integrated into a HERMLE C 40 5-axis machining centre. To fabricate a component using MPA technology, the material application is integrated with the established HERMLE machining technology, resulting in a hybrid manufacturing process. In addition to the conventional flat layer construction method commonly employed in additive manufacturing processes, the machine configuration also facilitates the build-up of material on curved free-form surfaces. The accessibility of component geometry for the application nozzle and the dynamics of the machine’s rotary and swivelling axes are limiting factors in this regard. For example, components can also be crafted in which a material coating is applied onto a rotating cylindrical blank.
Alternating material build-up layer by layer
With the MPA process, the material is always applied to the surface of geometrically accessible parts of the component. If other materials are incorporated or embedded in a component, the materials are built up alternately in layers to the extent that the respective contours of the other material are accessible for machining. The contour accuracy of the component depends on the milling method and can be adapted to individual requirements. Subsequently, the other material is applied to the prepared contours and milled back into the desired shape. In this manner, a solid body consisting of two or more materials can be created.
Filling material for ducts and hollow areas
Utilisation of a special filling material enables the realisation of inner hollow areas, ducts and undercut contours. The material is water soluble and flushed out at the end of the process to expose the inner geometry. Subsequent heat treatment optimises the microstructure and ensures the component has the desired hardness.
Production process
Demonstration of the production process using the example of a ball run
The component shown in the top left image was manufactured for demonstration purposes and contains a 3.4 m long duct (18x18 mm) along which balls can run, as well as an embedded copper insert, which highlights the HERMLE company logo through the final milled-out sections.
Component dimensions: 520 x 520 x 140 mm, total weight approx. 270 kg, of which approx. 40 kg were applied using the MPA process.
The sequence of images illustrates the main steps in the production process:
- Milling the duct into the prefabricated blank.
- Filling the milled duct with water-soluble filling material.
- Applying a top layer of 1.2344 hot-working steel. Milling the contours of the copper insert.
- Applying copper in a pre-milled contour, which is then milled back into the desired shape
- Applying another layer of 1.2344 steel. Finally, opening the view panel to the copper insert and removing any filling material still present in the duct.
Layer build-up during the MPA process
Both the powder particles from the nozzle and the surface of the substrate are plastically deformed upon impact with the substrate. Surface grains, in particular, undergo significant stretching and pressure, experiencing more than 10 Gpa and temperatures of up to 1,000°C at the boundary surfaces. This results in the formation of a binding contact surface between the particle and the substrate or the previously applied powder particles. Due to the plastic deformation, the component is heated isothermally, starting from the binding surfaces between the particles.
HERMLE Maschinenbau GmbH
HERMLE Maschinenbau GmbH based at the installation location in Ottobrunn, near Munich, is an affiliate of Maschinenfabrik Berthold HERMLE AG.
Over the years, the company has evolved into a customer-centric service provider, focussing on the advancement of the HERMLE MPA process with new materials/material combinations. We also provide extensive manufacturing capacities to produce components of varying sizes using the patented MPA process for our customers.
